This proposal aims to identify and validate novel circulating metabolic biomarkers to address critical, unmet needs in cardiovascular disease management. Our studies will specifically focus on myocardial ischemia and early injury, for which no suitable and clinically practical blood biomarkers presently exist. Our goal is to build on our initial observations and working hypotheses that an unbiased metabolomics discovery platform will yield novel biomarkers, and that simultaneous assessment of multiple biomarkers examining different pathophysiological axes will provide complementary information to improve diagnosis and clarify prognosis. Newly developed metabolomics techniques, richly-annotated clinical samples, as well as novel biomarkers already identified serve as the underpinnings for the proposed studies: In Specific Aim 1, we will use our LC- MS/MS-based metabolomics platform to identify novel early markers of myocardial injury in three unique cohorts of patients experiencing planned myocardial ischemia or injury: patients undergoing cardiac exercise stress testing with myocardial perfusion imaging, patients subjected to pacing-induced myocardial ischemia in the cardiac catheterization suite, and patients experiencing a planned myocardial infarction for hypertrophic cardiomyopathy. In Specific Aim 2, we will then characterize novel early markers of myocardial injury in carefully phenotyped cohorts of healthy controls, patients with stable coronary artery disease (CAD), and patients presenting across the spectrum of acute coronary syndromes (ACS). In Aim 3a, we will test the hypothesis that the novel biomarkers will aid diagnosis in two currently challenging clinical settings. First, we will test whether measurement of the biomarkers in patients undergoing exercise stress testing will enable the detection of inducible myocardial ischemia. Second, we examine whether measurement of the biomarkers in patients presenting to the Emergency Department with chest pain improves our ability to discriminate between non-ischemic chest pain versus unstable angina. In Aim 3b, we will test the hypothesis that the novel biomarkers will offer independent prognostic value beyond traditional clinical risk factors and established biomarkers in patients across several cardiac disease states including initial presentation with unstable angina and recent stabilization after ACS.